<?php
/**
 * crcl/base
 *
 * Copyright 2013 CRCL - André Sabosch - info@crcl.de
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

namespace crcl\base\instance;

interface ISingleton
{
  /**
   * Returns Instance. If instance not cached: creates it.
   *
   * @static
   * @return $oInstance
   */
  public static function getInstance();
  public static function singleton();

  /**
   * Removes cached instance
   *
   * @static
   */
  public static function removeInstance();

  /**
   * Checks if instance if cached
   *
   * @static
   * @return bool
   */
  public static function isInstance();
}

abstract class Singleton implements ISingleton
{
  public static function getInstance()
  {
    return self::singleton();
  }

  public static function singleton()
  {
    $sClass = \get_called_class();
    if (\is_null(self::$oInstance))
    {
      self::$oInstance = new $sClass;
    }
    return self::$oInstance;
  }

  public static function removeInstance()
  {
    self::$oInstance = \NULL;
  }

  public static function isInstance()
  {
    if (!\is_null(self::$oInstance))
    {
      return \TRUE;
    }
    return \FALSE;
  }

  /* PRIVATE **************************************************************************************/

  private static $oInstance = \NULL;
}